(ěs'kər) A long, narrow, steep-sided ridge of coarse sand and gravel deposited by a stream flowing in or under a melting sheet of glacial ice. Eskers range in height from 3 m (9.8 ft) to more than 200 m (656 ft) and in length from less than 100 m (328 ft) to more than 500 km (310 mi).